Does anyone know a good comprehensive resource to compare different base and specialty grains and their resulting flavor profiles?
I agree with brewchez. But, here's a good listing if you still want it.
Everyone's palate is different and the subtleties between the malts will be different person to person. I recommend planning out several mini batches and mini mashes of just the base malts to really get into it. I'd also say that making a big batch of simple extra light extra malt and steeping 0.5-0.75 lbs of specialty malts in one gallon batches to get a library of specialty malt flavors going too.
I've been brewing for >12 years and everytime I taste a malt closely, I seem to have a different take on it then what I have just read about it alone.